Do it all at once in preparation for Go 1.18 support.
To make this commit, I've simply modified the `fmt-check` Makefile
target to rewrite files instead of listing the differences. So this is a
fully mechanical change, it should not have introduced any errors.
In the early days of TinyGo, the idea of `postinit` was to enable
interrupts only after initializers have run. Which kind of makes
sense... except that `time.Sleep` is allowed in init code and
`time.Sleep` requires interrupts to be enabled. Therefore, interrupts
must be enabled while initializers are being run.
This commit simply moves the enabling of interrupts to a point right
before running package initializers. It also removes `runtime.postinit`,
which is not necessary anymore (and was only used on AVR).
There were a few issues that were causing qemu-system-arm and
qemu-system-riscv to give the wrong exit codes. They are in fact capable
of exiting with 0 or 1 signalled from the running application, but this
functionality wasn't used. This commit changes this in the following
ways:
* It fixes SemiHosting codes, which were incorrectly written in
decimal while they should have been written in hexadecimal (oops!).
* It modifies all the baremetal main functions (aka reset handlers) to
exit with `exit(0)` instead of `abort()`.
* It changes `syscall.Exit` to call `exit(code)` instead of `abort()`
on baremetal targets.
* It adds these new exit functions where necessary, implemented in a
way that signals the correct exit status if running under QEMU.
All in all, this means that `tinygo test` doesn't have to look at the
output of a test to determine the outcome. It can simply look at the
exit code.
